The invention relates to a suspension device and a rapping mechanism for vertically mounted electrodes, preferably rod-shaped, tubular, helical or plate electrodes in a high-voltage supplied electrostatic precipitator for the cleaning of smoke gases from the combustion of fossil fuels, waste material and the like in industrial plants, such as for instance power supply plants, combustion plants, cement plants and the like.
During filtration of smoke gases in such electrostatic precipitator an electrical high-voltage field is established between the collecting and discharge electrodes of the precipitator, in which field an ionisation of the dust particles passing through the precipitator occurs. Some of the particles charged thereby travel towards the collecting electrodes and the oppositely charged particles travel towards the discharge electrodes due to the corresponding opposite polarity in the relevant electrodes and there they accumulate, thus necessitating periodical vibration or rapping of the electrodes to remove the accumulated particles.
The discharge electrodes are metal electrodes and generally rod-shaped, tubular or plate electrodes or consist of wire helices and are suspended between a conductive top and a conductive bottom frame which may be connected by means of a vertical frame construction which is also conductive. The aggregate frame construction, together with a corresponding frame construction for the collecting electrodes which are generally plate electrodes, in the precipitator is surrounded by a precipitator housing to which the frame constructions are secured. The rod-shaped, tubular or plate discharge electrodes may be provided with a number of rod- or bow-shaped protrusions over their entire length to increase the corona discharges and thus to increase the precipitator effect when the precipitator is in use. In the hitherto known electrostatic precipitator types, e.g. SE patent No. 224,799, the frame is constituted by a comparatively heavy construction in order to support the suspended electrodes. The frame is suspended by means of vertical rods in insulators which are mounted in or on the precipitator housing roof, and may furthermore be connected to the supporting construction of the housing by means of inserted insulators and helical, plate or leaf spring mechanisms in order to limit the transfer of rapping or vibration energy from the electrodes to the housing and the insulators.
A bottom frame may, in addition to securing the electrodes at their lower ends, serve to maintain a convenient spacing between the discharge electrodes and the collecting electrodes to prevent the discharge electrodes from oscillating towards the collecting electrodes, thereby releasing a spark discharge. Such spark discharge temporarily reduces the electrical energy in the electrode spacings and impairs the precipitator efficiency. Often, the known precipitator constructions have the disadvantage that due to the comparatively excessive length of the electrodes the bottom frame oscillates back and forth relative to a top frame, thereby increasing the risk of sparkover between the electrodes.
The rapping mechanism for discharge electrodes in the known precipitators usually comprises electrically or pneumatically operated impact means, e.g. drop hammers, which are caused to rotate about a horizontal axis mounted above the precipitator housing, or weights on a crankshaft mounted horizontally in the same place. The impact means is brought by their rotation to abut anvils which are, in a number corresponding to the number of hammers or weights, secured to the top frame. Thus the top frame will absorb a portion of the impact energy produced which will, instead of being transferred in its entirety to the electrodes, partly be transmitted to the precipitator housing construction irrespective of any damping means optionally inserted between the latter and the frame.
It is therefore the object of the present invention to provide an assembly of a suspension device and a rapping mechanism for electrodes in an electrostatic precipitator, in particular the discharge electrodes of such precipitator, which remedies the above-mentioned disadvantages of the hitherto known precipitators.